Switching between comments and articles is conceptually one task. You are essentially changing the content. Switching between full-pane and split content is a different use context. I think it'd be better to split them. Have one toggle that uses a full-pane view with entirely content (and show another button that switches between article and comments), one toggle that provides a vertical split, and another that shows a horizontal split (the last two options would hide the prior option to switch views).

The current options make the user decide both the view layout and the content.

-The left panel view pretends to be loading something, but it's not.
It would be better to make a fallback to the last subreddit user was on
http://cl.ly/1S0h0K3O1e2B382R432l
-Also the textfield showing up when pressing cmd+G should resign if one chooses something in left panel view.

The lozenge button at the bottom of the window to change to different subreddits isn't in keeping with the Mac-style. A pop-up button or pull-down list would be more in keeping with the Mac experience. Also, the slider for "Hot/New/Controversial" doesn't animate like the switch between comments/views.